Copy options object so that we can confidently modify it

The options object was being modified by adding paths to it. This is a problem when the options object is reused later.

    // Options for specifying the style (green border
    // and semi-transparent green background)
    var polygonOptions = {
      "strokeColor": "#228b22",
      "strokeOpacity": 1,
      "strokeWeight": 3,
      "fillColor": "#228b22",
      "fillOpacity": 0.3
    };

    // Create a google maps object from geojson. During
    // the processing, our options object wasn't being
    // copied but instead modified by adding paths to it
    var polygon = new GeoJSON(geoJsonData, polygonOptions);

    // Later when we update an existing polygon to
    // change it's style to green, it's shape and paths
    // are also changed because the options object now
    // contains path data from the last time it was 
    // used by GeoJSON
    otherPolygon.setOptions(polygonOptions);

This pull request fixes the issue by copying the options object before it gets modified with path data.